This invention relates to a printing device like an ink jet printer for ejecting ink onto roll paper for printing. More specifically, this invention relates to a printing device for detecting type of roll paper loaded, the presence or absence of the roll paper, the leading end of the roll paper, and a preferable roll paper to be used in a printing device.
Nowadays, it has become possible for everybody to easily perform image printings thanks to the progress of computers and printing devices. Among the characteristic examples of printing devices is known an electrophotographic copier which causes a toner to adhere onto an electrostatic potential image formed on the paper roll and transcript the toner image onto the printing paper, a printing device which is called an ink jet printer of the aforementioned ink jet type or a printing device which is called a thermal transfer printer of a thermal transfer type which is adapted to melt the ink on the ink ribbon by means of a heated thermal head or cause the heat sensitive paper to be colored.
While color printing in general is required to have a good color tone quality and wheatherproofness, a wide application of printing media varing from paper, cloth, film or the like is seen and in order to maintain a printing quality in an excellent condition, the printing conditions are in general subjected to review on the basis of the type or property of a printing medium.
While it is possible to discriminate types of paper used through its factors such as surface roughness, light transparency and rigidity, but it is not practical to mount detection mechanism for that purpose upon printing device, because one detection device is necessary for anything of said paper factors, thus increasing considerably the cost of printing device. When detecting type of paper using the factor of light transparency, only three states of paper, i.e. transparent, translucent and opaque, which limits adaptation to more and more various types of paper. As described above, direct detection of paper type has been difficult in technical and economical view points.
In general, users of printing device have input the type of paper used into printing device by any means. One of these means has been setting of the type of paper on the operating panel of printing device by user. More recently, the information about type of paper to be used is often transferred into printing device from personal computer together with printing data. In the last case, user selects his desired type of paper from Paper Menu printed on a software called Printer Driver containing types of paper such as common paper, coat paper, film for a overhead projector (OHP), back print film, burnished paper and the like.
In addition, it is essential to set printing paper sheets neatly on the printing device. If not, it is not only impossible to maintain the printing quality but also likely to lead to the trouble in which the printing head can rub the printing face of the paper sheet or perform the printing action without the printing paper sheet being fed onto the platen with the result that the paper sheet is stained or the printing head and the platen are damaged to lead to the trouble of the printing device.
Therefore, it is required in general to refrain from performing a printing operation when the printing paper is not set properly or has run out.
In the case of a printing device which uses a long roll paper which necessitates a paper cut mechanism for cutting off the roll paper, it is often observed that an immediate start of the subsequent printing operation after the paper cutting operation to create an extra margin on the leading end of the paper sheet, which must be thrown away. This is not only a waste of paper but also another cutting operation must be done after the subsequent cutting of the roll paper, causing a duplication of work.
In such conventional method of using the roll paper, the roll paper payed out from the paper roll is fed in an opposite direction to the regular feed direction to reduce a margin space in the leading end of the paper as much as possible.
On the other hand, while there are several cases where one can easily discriminate paper used by means of appearance thereof and touch feeling thereon, there are so many papers which have resembling appearance and feeling. Therefore, users erroneously set different types of papers such as common paper and coat paper, both of which have same color at a glance, though they have quite different colors when reviewed carefully.
In case where the printing device is constructed such that it performs the printing operation by switching the printing conditions in accordance with the type of printing paper to be used, printing can be done on a condition other than suited for the paper if the operator makes an erroneous setting concerning the type of printing paper with the result that the printing quality desired by the operator cannot be obtained. Further, if the operator uses a printing device of the ink jet type which for example can perform a printing operation in not prescribed ink quantity for some type of printing paper. In this way, if setting is done on the basis of a wrong type of paper, extra ink used can adhere to some portions of the printing device to such an extent as thus staining the printing device or the printing paper.
Detecting devices used in a conventional printing device are known as a lever type, an optical type, etc.
In said lever type printing paper detect mechanism, the lever position varies depending upon the presence or absence of the printing paper and said varied lever position is detected as ON/Off signals of the switch. On the other hand, an optical type paper detection mechanism includes a reflection type in which a light irradiated by the light emitting portion onto the paper to be reflected thereby is detected by the light receiving portion and a transmission type in which a light transmitted is detected by a light receiving portion positioned opposite the light emitting portion.
In said optical paper detection mechanism of reflection type permits the variation of the intensity of reflection of the light irradiated by the light emitting portion on the basis of the presence or absence of the printing paper to be converted into the variation of the electrical output for detection. On the other hand, the optical paper detection mechanism of transmission type converts into the variation of electrical output the variation of intensity of light determined depending on whether or not to interrupt the light irradiated by the light emitting portion on the basis of the presence or absence of the printing paper.
In the conventional printing paper detect mechanism, it is possible to detect the presence or absence of the printing paper regardless of the light transmitting property whether transparent or opaque if the mechanism is of a lever type. However, such mechanism has a problem that it is necessary to bring the lever in contact with the platen by way of the printing paper in order to detect the presence or absence of the printing paper at the printing portion, causing the lever to contact the platen directly if there is no printing paper thereat with the result that the platen can be damaged. Therefore, an optical paper detect mechanism of reflection type is used in general as a paper detection mechanism.
Such optical paper detection mechanism of reflection type has another problem that it is impossible as is to detect the presence or absence of the printing paper if the paper is a light transmitting transparent sheet such as OHP paper. Then, a light reflecting opaque portion is formed at an end portion (said end portion taken in a direction perpendicular to the paper feed) of the transparent sheet so that said opaque portion reflects the light to be detected. However, such method also has a problem that the opaque portion at the end of the printing paper makes it impossible to effectively use the entire surface of the printing paper and makes the opaque portion too conspicuous to prevent the printed image from viewed easily when projected by an over head projector.
Further, excessive rewinding of the roll paper in the user""s attempt at saving the paper or any possible misalignment of the leading end of the roll paper upstream of the correct position of printing portion can cause a printing action to be performed against the platen or cause a clogging of paper as a result of excessive rearward feed.
In view of the above points, it is the object of the present invention to provide a printing device which is capable of automatically detecting the type of the roll paper.
It is another object of the present invention to provide a printing device which is capable of effectively detecting the presence and absence of the roll paper formed of a light transmitting transparent sheet by means of an optical printing paper detect mechanism and a roll paper which is detected in a favorable condition by the optical printing paper detection mechanism.
It is a further object of the present invention to provide a printing device which is capable of automatically detecting whether or not the leading end of the roll paper fed for the printing operation is positioned properly when the roll paper has been rewound in order to prevent an extra margin from being formed.
In order to achieve the aforementioned object, a printing device according to claim 1 is characterized by a holder engaging member which is movable and can be applied onto peripheral surface of the flange of said holders of said paper roll held by said paper roll holding mechanism, by a paper type detection unit for detecting type of said roll paper according to the position of said flange engaging correspondingly to outer diameter of said flange representing type of said roll paper used, by a paper presence/absence detection unit for detecting the presence or absence of said roll paper without contact therewith is located in said printing portion so as to oppose to said platen, by a paper leading end detection unit for detecting the leading end of said roll paper is located between said printing portion and a cutting portion, and control means for controlling actions of the relevant portions on the basis of the detection result of each detection unit.
In such a construction, said paper type detection unit can automatically detect type of paper only by amounting a flange, outer diameter of which is adapted to type of roll paper, said paper presence/absence detection unit can automatically detect the presence or absence of said roll paper without contact therewith, said paper leading end detection unit can automatically detect whether the paper leading end of said roll paper is in a appropriate position or not, and control means can control appropriate actions of the relevant portions on the basis of the detection result of each detection unit.
The printing device according to claim 2 is characterized in that the detecting unit of paper presence/absence is composed of a photosensor while the control means is constructed to determine the paper type by reversing information from the photo sensor on the basis of a result whether or not light transmission.
By adopting the aforementioned construction, the it is possible to automatically detect the presence/absence of the roll paper by means of the photosensor notwithstanding the result as to whether or not the roll paper is of light transmitting nature.
The roll paper according to claim 3 is characterized by being formed of a light transmitting transparent sheet and having a light reflector at the trailing end thereof.
By adopting the aforementioned construction, it is possible to effectively use the entire surface of the roll paper if said roll paper is formed of a light transmitting transparent sheet and said light reflector of the roll sheet is capable of automatically detecting the presence/absence of the paper.